The possibility of detecting the simultaneous occurrence of an event at a plurality of electronic devices may be of advantage for various applications.
In order to detect a simultaneous occurrence of a specific event at a plurality of electronic devices, the electronic devices have to notify each other about an occurrence of the event at their side. Many utilizable communication links, however, are not instantaneously available for transferring such a notification between electronic devices.
An application for which the detection of a simultaneous occurrence of an event at a plurality of electronic devices might be used is, for example, an exchange of data between the electronic devices using a direct wireless connection.
It is known to enable a direct wireless transfer of data between two electronic devices, for instance for exchanging business cards between two mobile phones. The transmission channel can be realized for instance by Bluetooth™ (BT), by means of infrared (IR) ports or by means of a Wireless Local Access Network (WLAN), or by manufacturer or industry specific protocols.
In conventional solutions, the activation and initiation of a direct wireless data transfer between two electronic devices is often considered to be complicated or annoying. Therefore, it has been proposed to enable an ad-hoc connection between two electronic devices. For such an ad-hoc connection, it is determined whether two electronic devices undergo a specific motion pattern relative to each other while being at least in close vicinity to each other. In this case, a data transfer channel is opened as a local wireless link for transferring data between the electronic devices, without any preceding complex user input. This approach has been described for example in U.S. patent application Ser. No. 10/390,548, filed on Mar. 14, 2003, which is incorporated by reference herein.
In order to ensure that the relative motion pattern is indeed achieved between two electronic devices between which an ad-hoc connection is possible and intended, it would be of advantage to verify whether the motion pattern is experienced at two electronic devices at the same time.
In case two electronic devices are connected to each other by cable, verification can be achieved by an immediate exchange of signaling data. Such devices are for instance able to handshake with wired signaling or to create interrupts to a host system which entered a power saving mode. One example is the RS-232 standard serial port in a PC, which can be employed.
If data has to be exchanged between the electronic devices using a wireless connection, however, such as a Bluetooth™ or an IrDA® (Infrared Data Association) connection, a data transmission channel initiation phase has to follow an appropriate protocol, which takes up a considerable amount of time. The caused delay prevents an instant data transmission. With Bluetooth™, the delay can be several seconds in the worst case.
Bluetooth™ enables the use of a so called ‘sniffing-mode’, in which a Bluetooth™ enabled device periodically listens to potential data senders. It is a disadvantage of this mode, though, that the Bluetooth™ module of a device consumes a considerable amount of power. A continuous listening mode thus reduces the operation time of the electronic device and is therefore not suited for exchanging notifications about a detected motion pattern.
Also with other types of connections, the employed data transmission means can typically not remain switched on all the time, since the power consumption and the device operation times should be kept low.
When existing network connections are used to exchange data between electronic devices, delays are involved as well, in addition to possible costs.
Common asynchronous or packet-switched data synchronization methods have the disadvantage that they require real time availability of the data transmission channel.
In general, the use of wireless connections between electronic devices thus makes an immediate signaling of an experienced motion pattern impossible.
If a notification of an experienced motion pattern is exchanged between electronic devices with a delay, the time of occurrence of the motion pattern has to be indicated as well. The internal clocks of the involved electronic devices might be set to different time zones or to different daylight saving settings, though. Further, the clock of one or more of the involved electronic devices might not be set accurately or work inaccurately, that is, the clock of one device might be running faster than the clock of another device. This makes the indication of a comparable instance of time difficult.